Patent GB-286243-A (GB)
Title: Improvement in elevator safety system
IPC: B66B5/18
Filed: 1928-01-05
Abstract: 286,243. Waygood-Otis, Ltd., (Assignees of Lindquist, D. L.). March 1, 1927, [Convention date]. Cage lifts; catch gear and like safetyretaining mechanism. -In a balanced lift system the sheave around which passes the lower rope connecting the cage and counterweight is permitted only a limited movement in the upward direction for the purpose of stopping the continued movement of the counterweight after the cage has been brought to rest. The amount of movement of the sheave which is permitted is only sufficient to compensate for changes in the length of rope due to the temperature, humidity, &c. In one construction the sheave 27, Fig. 6, is mounted in a frame 124 provided with guides 128 which engage vertical angle bars 130, 131 secured to the bottom of the well. Racks 137, 138 formed on the angle bars are engaged by pawls 140, 143 mounted on the top of the frame. The outward movement of the pawls is limited by the engagement of ther flat bottoms, Fig. 8, with the frame. In another construction helical springs are interposed between the frame carrying the sheave and a crosshead which can move downwards along vertical guides but is prevented from moving upwards by wedges. Safety brakes 35, 36, Fig. 1, atached to the cage are applied to the guides 30 if the speed becomes excessive during descent. These brakes are of the type which may be released by upward movement of the cage. The actuation of the brakes is controlled by a governor 38 driven by a rope 40 which is attached to the arm 41 of a bell-crank lever 42 pivoted to the cage and normally prevented from turning. The other arm 43 of the lever is attached to the lock bar 60 of a releasing carrier 44, Fig. 2. The rope 40 passes between pivoted jaws 48, 50 which are geared together. An extension 54 of the jaw 48 is engaged by a spring-pressed latch 56 and is attached to a link 55 of the governor. The jaw 50 is pivotally mounted on a rod 51 slidably mounted in guides 52 and controlled by a spring 53. When an overspeed occurs, the pull on the link 55 overcomes the resistance of the latch 56, and the jaws are released. The jaws fall and grip the rope with a pressure determined by the strength of the spring 53. The movement of the rope is therefore retarded, and the lever 42 is rocked to effect the application of the brakes. The lock bar 60, Fig. 2, is provided with a boss 62 having a recess 64 in which a jaw 63 is yieldingly maintained by a spring 65 mounted on a bolt 66. The arm 41 is connected by a rod 67 to the actuating lever 68 of the brake 35. This lever is keyed to a shaft 69 which extends below the cage to the brake 36. Each brake comprises jaw members 73, 74, Fig. 3, pivoted on a vertical shaft 75. A wedge 78 is mounted on the jaw 73 opposite the guide 30 so that it can swivel and is engaged by a roller 85 mounted on the lever 68. A wedge 93 slides on the'part of the jaw 74 opposite the guide 30 and is connected thereto by a dovetail joint. The wedge is urged upwards by a spring 96. A compression spring 102, Fig. 4, is arranged on a bolt 103 between the ends of the jaw members 73, 74 away from the guide. Means are provided for varying the tension of this spring. When an overspeed occurs the shaft 69 is rotated and the roller 85 is forced upwards between the guide rail and wedge 78 . This movement of the roller turns the jaw member 73 about the shaft 75 and this movement is transmitted by the spring 102 to the jaw member 74. The movement of the member 74 brings the wedge 93 into engagement with the guide rail. Continued upward movement of the roller 85 causes an increasing compression of the spring 102 and a corresponding increase in the braking force exerted by the roller and wedge on the guide rail. As the shaft 69 turns a cam 16 on it engages the actuating lever 17 of a switch 39 which effects, the cuttings-off of current from the hoisting motor 22 and the application of the electromagnetic brake 23. An oil buffer 34 for the counterweight is suspended below. An oil buffer for the cage is mounted at the bottom of the well.